Listen Technologies 863 .050 User manual

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Design Guide LT-800 LR-400/500 Supplementary
Design Guide
FM Technology Overview 5
System Overview 6
Key Concepts in Designing an FM System 8
Notes 17
LT-800 Stationary FM Transmitter
Specications 25
Block Diagram 26
Quick Reference 27
Setup Instructions 28
Operating Instructions 30
Accessories 34
Notes 35
LR400/500 FM Receivers
Specications 45
Block Diagram 47
Quick Reference 48
Setup Instructions 50
Operating Instructions 53
Programming Instructions (LR-500 only) 59
Accessories 60
Notes 61
Supplementary Information
Battery Charging Information 69
Frequency Chart 70
Troubleshooting 71
Frequently Asked Questions 73
Compliance, Warranty and Contact Information 75
Notes 76
Stationary FM Table of Contents

1

3
Design Guide
Stationary FM Design Guide Table of Contents
Table of Contents 3
Technology Overview 5
System Overview 6
Key Concepts in Designing an FM System 8
Notes 17

5
Design Guide
Frequency Modulation (FM) Technology Overview
Frequency modulation or FM is a means of transmitting audio using electromagnetic waves.
This same technology is used by local FM radio stations to broadcast music. FM signals can travel through
most barriers – walls, oors, and ceilings. The distance a signal travels has many different variables such as
Radio Frequency (RF) output power, the type and placement of the antenna, and the broadcasted
frequency. Unlike infrared, FM transmission are not secure. This enables a receiver to travel further distances
from the source. This section of the manual will help you design a system that will get the best range and least
amount of interference.
Audio Source
FM Transmitter
Receiver
When designing an FM system it is important to keep the following in mind:
• Multipath
Multipath distortion is a form of RF interference that occurs when radio signals have more than one path between
the receiver and the transmitter. This could occur in rooms with metallic or other RF-reective surfaces, such as
furniture, walls, or coated glass. The result of multipath is the receiver signal coming in and out of squelch when the
receiver is moved. Portable applications are much more susceptible to multipath than those that are stationary.
Multipath could be worse as the distance between transmitter and receiver increases (RF power decreases).
Multipath can decrease the audio quality of the transmission.
• Antenna placement
The antenna should be placed as high as possible and in line of sight of the receivers. The antenna should not be
mounted near metal objects. Keeping the coaxial cable as short as possible will also limit the loss of RF power.
The LT-800 comes equipped with an articulating right angle dipole antenna (LA-129). The remote antenna kit
(LA-130) is an optional accessory. The antenna on the receivers should always be in the upright position to maximize
the transmission range. Placing the antenna in areas where the RF cannot properly be transmitted will limit the range
of transmission.
Design Guide

6
Design Guide
System Overview
There are four main parts to a Stationary FM system – transmitter, antenna, receiver and input source, .
The input source can be audio from a sound board, microphone or a personal audio source like a CD player,
MP3 player, computer, DVD, etc. Audio will be Connected into the audio inputs of the stationary transmitter.
Input Source
LT-800 Stationary FM Transmitter (863 MHz)
Input source
LR-500 Portable
Programable Display FM
Reciver (863 MHz)
LR-400 Portable
Display FM Reciver
(863 MHz)
The LT-800 transmitter modulates the audio on an FM carrier and transmits the signal via an antenna.
Transmitter
LA-129 Articulating Antenna
LT-800
LA-130

7
Design Guide
Input source
System Overview
There are a several options for antennas. Antennas can either be back-mounted on the
unit or remote mounted.
Antenna
Listen offers two different portable receivers, the LR-400 and LR-500.
Receivers
LA-131 Antenna Kit for Rack Mount (863 MHz)
LA-130 Remote Antenna Kit (863 MHz)
LR-500 Portable
Programable Display FM
Reciver (863 MHz)
LR-400 Portable
Display FM Reciver
(863 MHz)
LA-129 Articulating Antenna

8
Design Guide
Connect the audio source(s) to one or both audio input connections. Input 1 offers a choice of balanced
XLR or ¼” phono connector. Plug your microphone into Input 1 and move the input select switch to Mic (for
dynamic microphones) or Mic + PH Power (for condenser microphones). A feed from a soundboard can also
used with Input 1. Be sure the input type selected (line, mic or mic-PH PWR) matches with the output type ofv
to be the mixing board. Plug your balanced or unbalanced audio source into Input 1. Use the following
diagram:
Key Concepts in Designing a Stationary FM System
Input Selection
Unbalanced right
and left phono
connectors
XLR Wiring
Input from
Balanced
Audio
Source
Unbalanced
Audio
Source
1/4”Phone Wiring
Balanced
Tip
Ring
Sleeve
Unbalanced
Top Ring Top Ring/Sleeve
Audio from
Balanced
Audio
Source
Unbalanced
Audio
Source
Sleeve
Input 1: Connect the audio source(s)
Balanced XLR or
1/4” phono connector
The LT-800 has two audio input options: Input 1 and Input 2. Input 1 is a balanced connection using either an XLR or ¼”
phono connector. The LT-800 has two audio input options: Input 1 and Input 2. Input 1 is a balanced connection using
either an XLR or ¼” phono connector. Use Input 1 if you are using a microphone or if you have a balanced connection
such as from a professional audio mixer (you can also use Input 1 for unbalanced connections). Use Input 2 to connect
to an unbalanced audio source.

9
Design Guide
Key Concepts in Designing a Stationary FM System
Plug your unbalanced audio source into Input 2 and select the audio level switch for -10dBu or +10dBu, to
match the audio level coming from your equipment.
Input 2: Connect the audio source(s)
The LT-800 can accomdate inputs simultaneously with the use of the input level potentiometer.
When two inputs are present, both sets of input level lights will be activated.
Using Two inputs
Mix Level
The mix level acts as the “master transmit” control. It will increase the transmit gain on the “mix” of the two
levels (if two levels are in use).
Mix level adjustment
Input level

10
Design Guide
Test tone
Use the test tone to transmit a 1 kHz tone. This tone will allow the end user to know if the system is transmitting
properly. All receivers should be able to hear this tone if tuned to the proper channel.
Test tone button
Selecting Transmitting Frequencies
Use this section of the guide to choose the channel settings for the transmitter and receivers.
Find transmission channel(s)
The goal is to nd a transmission channel(s) that is free from interference. Interference comes from other
transmitters and from other equipment (such as a computer).
Listen’s LT-800-863 oers 17 dierent channels to choose from
Listen’s LT-800-863 offers 17 different channels to choose from. This increases the chance you’ll nd an
interference free channel. The best way to check for interference is to turn a receiver on and press the SEEK
button. If there are any channels with interference, the receiver will nd these channels.
Testing system
Monitor Jack
The headphone jack is used to monitor the mix of input 1 & 2. You can adjust the monitor level with the volume
knob. The headphone jack is a standard 3.5mm jack.
Headphone
monotoring jack
Key Concepts in Designing a Stationary FM System

11
Design Guide
Key Concepts in Designing a Stationary FM System
Antenna placement (rear or remote)
Rear mounted antenna
Rear mounting the LA-129 will allow the transmitter to be moved if necessary.
Remote antenna
The LA-130 Remote Antenna Kit connects to the LT-800 and can be placed away from the transmitter for better
range. It also allows the unit to be rack mounted with the antenna remotely using the LA-326 Universal Rack
Mounting Kit. The LA-130 comes with 25’ of black coaxial cable (RG-58)
ATTENTION: Long cable runs can result in signal degradation due to the “loss” characteristics of
the cable. Minimize cable runs as much as possible or use “low loss” RG-8 cable.

12
Design Guide
Key Concepts in Designing a Stationary FM System
Front of the rack mounted antenna
The antenna can also be in the front of the rack with the use of the LA-131 Antenna Kit for Rack Mount
(863 MHz) and the LA-326 Universal Rack Mounting Kit.
For proper and dependable operation, Listen receivers need to receive a strong and consistent signal from the
originating transmitter. The following strategies should be used maximize this signal:
Maximizing Transmission Range
Transmitting and receiving antennas
When designing and installing your system, keep in mind that the location of both the transmitting and
receiving antennas is critical to maximize broadcast range. Eliminate or minimize obstructions between the
transmitting and receiving antenna. Minimize the distance between the transmitting and receiving antennas.
Move transmitting and receiving antennas away from metal or conductive objects.
Antenna Placement
Place the transmitting antenna as high as possible.

13
Design Guide
Key Concepts in Designing a Stationary FM System
Orientation
Orient both transmitting and receiving antennas vertically.
RF Power switch
Position the RF Power switch on the back of the LT-800 to full RF Power, unless lower power is necessary.
Cable Length
Keep coaxial cable from transmitter to antenna as short as possible.
CAUTION: When installing antennas, ensure the antenna is clear of power lines.
RF Power Switch

14
Design Guide
Key Concepts in Designing a Stationary FM System
Mounting Transmitter
The LT-800-863 can be rack mounted if necessary. With the use of the Listen LA-326 Universal rack mounting kit,
you can mount one or two transmitters to the standard 19” rack. The rack mounted unit will take 1ru of space
Rack Mount with dual units installed.
The LA-131 rack mount accessory will allow you to place your LA-129 antenna at the front of the rack. Having
the antenna in the front will give better reception range.
NOTE: The antenna may need to be remote mounted using the LA-130 Remote Antenna Kit if the
transmitter(s) is rack mounted. If a rack is metal, it is not recommended to have the antenna inside. Also,
the depth of the rack and equipment inside could prevent an antenna from being placed inside.
Rack Mount with single unit installed.